As noted by Sequeira (110,111), the term recognition has become very popular in the literature of host-pathogen interactions over the last ten years. Despite recent facile usage, its meaning is not always clear to me. Recognition is defined by Clarke & Knox (16) as the initial event in cell-cell communication that elicits a defined biochemical, physiological, or morphological response. This requires the not-so-easy task of defining initial event and communica tion with precise chemical or physical mechanisms. For pathologists, Se queira (110) has provided a more restricted meaning: An early specific event that triggers a rapid, overt response by the host, either facilitating or impeding further growth of the pathogen
